The human organism is not capable of the oxygen in the air not to use.
75% of the oxygen that we breathe, unconsumed occurs again and the 21% oxygen,
in exhaled air are included, the human organism can only use about 25%.
This also explains why report a resuscitation by mouth-to-mouth resuscitation is useful.

Supplementary oxygen for energy production would not help. The human organism can not use it anyway. In addition, the elderly and physically in a bad constitution, the ability for optimal oxygen utilization decreases.

So it is not enough oxygen or the concentration, but the ability of our body, the oxygen in the cells to be able to use.

Humans need energy. What can you do?
You do not increase the quantity of oxygen to the body is inserted, but the quality.
It's like a motor: only promotes optimal combustion performance.